The present invention relates to methods for using proteins which function in controlling development, differentiation, trafficking, and physiology of mammalian cells, e.g., cells of a mammalian immune system. More particularly, it provides methods using proteins and mimetics which regulate cellular pulmonary inflammation and methods of treating diseases or conditions associated with Th2-mediated hypersensitivity states, such as asthma.
The present invention also relates to genetically engineered non-human animals and their use as molecular models in the study of the CCR8 chemokine receptor and molecules affected by the action of CCR8.
The chemokines are a sub-family of chemoattractant cytokines that were classically characterized by their ability to mediate leukocyte trafficking by binding to specific G-protein linked seven transmembrane spanning receptors, or GPCRs [Baggiolini et al., 1998, Nature 392:565-568]. This activity, and the observance of chemokine production in diverse inflammatory settings, has implicated chemokines as mediators of immune and inflammatory responses [Sallusto et al., 1998, Immunol. Today 19:568-574; Moore et al., 1998, J Lab. Clin. Med. 132:97-103; Tabu et al., 1996, J. Immunol. 156:2095-2103]. Chemokine receptors transduce signals important for the development and trafficking of specific leukocyte subsets. [Rollins et al., 1997, Blood 90:909-928; Premack et al., 1996, Nat. Med. 2:1174-1178; Murphy et aL, 1994, Ann. Rev. Immunol. 12:593-633]. In order to help clarify the physiological function of the chemokines and their receptors, recent efforts have focused on defining the cellular expression and distribution of chemokine receptors. To date, several of these G-protein coupled receptors have been characterized and evidence suggests that they are differently expressed among leukocyte populations. [Mackay et al., 1996, J Exp. Med., 184:799-802; Locati et al., 1999, Ann. Rev. Med. Med. 50:425-440]. In particular, lymphocyte subpopulations are reported to display restricted expression of chemokine receptors, raising the possibility of receptor-based immune manipulation [Oppenheim et al., 1997, Clinical Cancer Research 3:2682-2686].
CCR8 is a chemokine receptor [WO 99/06561] whose expression is primarily restricted to Th2 cells [Zingoni et al., 1998, J Immunol. 161:547-551; D""Ambrosio et al., 1998, J Immunol. 161:5111-5115]. Indeed, the ligands for this receptor, I-309 in humans and TCA3 in mice, are chemotactic for Th2 cells in vitro [D""Ambrosio et al., 1998, J. Immunol. 161:5111-5115]. The viral chemokines vMIP-1, vMIP-II and vMCC-1 have also been reported to have high affinity to CCR8: vMIP-1 acts as a CCR8 agonist [Endres et al., 1999, Exp. Med. 189:1993-8; Sozzani et al., 1998, Blood 92:4036-39], while vMIP-II and vMCC-1 act as potent antagonists [Dairoghi et al, J. Biol Chem 294(31):21569-74]. However, the in vivo function of CCR8 and its ligands is yet unknown.
Medical science relies, in large degree, on appropriate recruitment or suppression of the immune system in effecting cures for insufficient or improper physiological responses to environmental factors. However, the lack of understanding of how the immune system is regulated or differentiates has blocked the ability to advantageously modulate the immunological mechanisms to biological challenges, i.e., response to biological injury. Medical conditions characterized by abnormal or inappropriate regulation of the development or physiology of relevant cells, such as asthma, thus remain unmanageable. The discovery and characterization of specific regulatory pathways and their physiological effects will contribute to the development of therapies for a broad range of degenerative or other conditions which affect the biological system, immune cells, as well as other cell types. Understanding the role of immune cells and their overall finction in the development of various inflammatory conditions has been hampered by the lack of in vivo models. The present invention provides solutions to some of these and many other problems.
The present invention is based, in part, upon the discovery of the physiological role of the chemokine receptor CCR8 in various models of immune response. In particular, the role of CCR8 has been elucidated in pathways involved in Th2-mediated allergic responses, particularly asthma. This invention, therefore, provides methods of treating allergic or other diseases using agonists and antagonists of CCR8, as well as methods for screening for drugs useful in such treatment using CCR8 as a screening target. The invention also relates to the identification of a model system to study the role and function of CCR8 receptors through the use of genetically engineered animals which lack a functional CCR8 gene.
The present invention provides methods for treating a Th2-mediated condition in an animal, the methods comprising administering to the animal a therapeutic amount of an antagonist of a mammalian CCR8 receptor. Specifically, the invention provides methods for treating asthma in an animal comprising administering an antagonist of a mammalian CCR8 receptor. Preferred embodiments include where the antagonist is an antibody which binds to the mammalian CCR8 receptor, or where the antagonist is a small molecule inhibitor. Further embodiments include where the antagonist is a modified chemokine ligand. The administering may be in combination with: an anti-inflammatory agent; a cytokine agonist or antagonist including especially an antagonist of a Th2 cytokine such as IL-5, IL-13 or IL-4; an analgesic; a steroid or an antihistamine.
Also provided by the present invention are methods of screening for drugs useful for treating diseases associated with the immune response such as asthma. In a preferred embodiment, CCR8 is used as a target to screen for asthma therapeutics.
The invention also provides a genetically engineered non-human animal whose genome lacks a functional CCR8 gene, and methods for its use as a model for molecular mechanism.